Perkins Block 5/16 oil pan bolt stripped. Help!!

We are finishing up a Perkins A3.152 diesel rebuild. I went to put on the oil pan bolts ( 5/16" NF ) , and I found out that one was drilled or stripped by the machine shop. ( out of business now. ) We ended up drilling it out to 3/8 NF as the original hole was probably drilled out and not tapped or something. The hole was too big for a 5/16" bolt.

Anyway, we tapped it to 3/8" NF, but when we go to tighten the bolt, the threads on the bolt get chewed off. How do we fix this? Heli coil kit?

Help please because I really don't want to have to take it to a machine shop for repair.

Thanks in advance ,

Will

I agree with David. For the life of me, I do not know why MD used fine thread bolts into cast iron. Fine thread bolts have less thread engagement than course thread bolts and are not recommended for use in soft materials like cast iron.

If worst comes to worst, you can helicoil it. With patience, helicoils work well.

Dean

It is along the left side of the block, 2nd from ftont below the oil filter housing. We will try the 10mm course tap tomorrow.

Thanks,

Will